Arrangement in electric air blast circuit breakers



Oct. 13,v 1959 H FORWALD 2,908,788

ARRANGEMENT IN ELECTRIC AIR BLAST CIRCUIT BREAKERS Filed April 11, 1957 Fig Fig.2

7 INVENTOR. fvaa/con Tom/aid United States Patent ARRANGEMENT IN ELECTRIC AIR BLAST CIRCUIT BREAKERS Haakon Forwald, Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden In order to protect a high tension air blast circuit breaker against over voltages when the breaker is opened the series of main breaking gaps have been connected in parallel with a voltage equalizer built up by voltage dependent or voltage independent resistances. The resistances in the voltage equalizer have mostly been permanently connected to the contacts of the main breaking gaps, but it has also been proposed to arrange special auxiliary breaking gaps in series with the resistances. These auxiliary breaking gaps have been independent of the main breaking gaps and arranged apart from the main breaking gaps.

The present invention relates to a high tension air blast circuit breaker comprising one or a plurality of series connected main breaking (gaps which are arranged in metal containers normally carried by high insulating pillars, which containersare filled with compressed air when the circuit breaker is in service. The invention is mainly characterised in that at every main breaking gap a resistance and an auxiliary breaking gap is arranged between the metal container and one con tact of the main breaking gap insulated from the container and in that the resistance is connected to and carried by the wall of the insulated container and one of the contacts in the auxiliary breaking gap is connected to one contact in the main breaking gap insulated from the container. A very simple circuit breaker is achieved by this method. Insulating parts are saved in that in every metal container only one bushing insulator is necessary, namely a bushing insulator carrying one of the contacts of the main breaking gap and eventually one insulator, entirely enclosed in the container, which insulator carries one of the contacts of the auxiliary breaking gap.

In Figure 1, three series connected main breaking gaps having contacts, 1, 2, 3, 4, 5, and 6 are shown schematically. The contacts 1, 3, and are carried by bushing insulators 7, 8, and 9 which are inserted in the walls of the compressed air containers 10, 11 and 12. Within the compressed air containers the resistances 13, 14 and 15 are arranged, which, at their lower ends are connected to the contacts 16, 17 and 18 of the auxiliary breaking gaps. The other contacts 19, 20 and 21 of the auxiliary breaking gaps are connected to the contacts 1, 3 and 5. The other ends of the resistances 13, 14 and 15 are electrically connected to the walls of the containers 10, 11 and 12. The auxiliary breaking gaps 16-19, 17-20 and 18-21 are, in a manner not shown in the figure, operated in such a way that they are closed or will be closed before the main breaking gaps 1-2, 3-4 and 5-6 are opened.

Instead of connecting one end of the resistances permanently to the wall of the compressed air container and one of the contacts of the auxiliary breaking gap with one of the contacts of the main breaking gap, it is possible to connect one end of the resistance permanently with the said contact of the'main breaking gap ice and to connect one contact of the auxiliary breaking gap with the container.

In Figure 2 one embodiment of the circuit breaker according to the invention is shown schematically. In this embodiment the resistance is connected in parallel with the main breaking gap immediately before this is opened by closing the auxiliary breaking gap. This breaking gap is then reopened a short time after the current through the main breaking gap is interrupted. In Figure 2 a main breaking gap with a compressed air container, a resistance and an auxiliary breaking gap is shown. 22 is an air container in which a bushing insulator 23, carrying the stationary contact 24 of the main breaking gap is inserted. 25 is a resistance which is connected at its upper end to the container 22. This resistance and the operating mechanism 26 for the auxiliary breaking gap, is carried by the insulator 27. The operating mechanism consists of a piston 28, movably arranged in the cylinder 29, in which the spring 30 is arranged. The piston 28 is connected -to the movable contact 31 of the auxiliary breaking gap. The contact 24 of the main breaking gap is also used as the stationary contact of the auxiliary breaking gap. The movable contact of the main breaking gap consists of a cylinder 32 which is movably arranged in a stationary cylinder 33. The movable contact 32 is, by the piston rod 34 connected to a valve disc 35 having a sealing edge intended to seal against the ring 36. The exhaust valve consists of a cylinder 37 which is provided with a conical shaped upper end 38. This conical part is intended to rest against the sealing ring 39. 40 designates exhaust openings by which compressed air can escape from the container 22 to the atmosphere when the cylinder 37 and the movable contact 32 are moved downwards. The operating mechanism 26, connects through a pipe 41 with the space 42 which is closed by the piston 43 at its upper end connected to the cylinder 37. There is also a restricted or throttled pipe 44 which directly connects the container 22 with the space under the piston 43.

The circuit breaker works in the following way. It is opened when the rod 45 is pushed to the left and the valve disc 46 is moved away from the right valve seat so that the compressed air is free to pass to the right around the rod 45, and is thus allowed to escape from the space under the piston 43. The pipe 41 is then also emptied whereby the pressure in the container 22 actuating upon the piston 28 moves it to the left so that the contact 31 is brought into contact with the contact 24 although the spring 30 acts upon the piston in the opposite direction. When the valve disc 46 is moved and the outlet is thus opened, the pressure in the container 22, acting upon the conical part 38 of the cylinder 37, will force the piston 43 to move downwards against the force of the spring 47. Then the tubular contact 32 moves downwards against the force of the spring 48 until the valve disc 35 comes into contact with the sealing ring 36. Compressed air from the container 22 passes through the pipe 44 into the space 42 and moves the piston 43 upwards after the seating of the disc 35, so that the conical surface 38 is once more pressed against the sealing ring 39. When the piston 43 reaches its upper position air streams from the container 22 through the pipe 44 and the space 42 to the pipe 41 and into the cylinder 29 and the spring 30 then moves the piston 28 to the right so that the auxiliary breaking gap is opened. The main breaking gap is kept open as the pressure in the space 42 acts upon the upper 35.

The circuit breaker is closed by moving the rod 45 and the valve disc 46 to the right which results in the compressed air streaming from the container 22 through side of the valve disc 3 the pipe 49 to the lower side of the valve disc 35, so that this is moved upwards by the spring 48.

I claim as my invention:

A high tension air blast circuit breaker comprising an insulated metallic container for compressed air, fixed and movable main contacts forming a mainbreaking gap located within the said container, an insulator whereby one of-the two main contactsis electrically insulated from the container, a resistance enclosed in the container and electrically connected to and carried by the wall of 10 2,665,351

2,908,788 r I I said container, and an auxiliary contact co-acting with the said insulated main contact to form an auxiliary References Cited in the file of this patent UNITED STATES PATENTS Forwald Ian. 5, 195 4 

